Response of Kalahari vegetation to seasonal climate and herbivory: Results of 15 years of vegetation monitoring

Schmiedel, Ute; Jacke, Vasco; Hachfeld, Berit; Oldeland, Jens

doi:10.1111/jvs.12927

Cited by 11 publications

(9 citation statements)

References 59 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, large uncertainties prevail in understanding the African ecosystems and quantifying spatiotemporal variations of their functioning due to the complexity of continental gradient and scarcity of ground measurements. This has been shown in studies using different data and approaches ranging from in‐situ observations (Schmiedel et al., 2021 ), over remote sensing (Weerasinghe et al., 2020 ), to ecosystem modeling (C. Martens et al., 2021 ), as well as systematic literature reviews (Adole et al., 2016 ).…”

Section: Introductionmentioning

confidence: 87%

Characterizing the Response of Vegetation Cover to Water Limitation in Africa Using Geostationary Satellites

Küçük

Koirala

Miralles

et al. 2022

J Adv Model Earth Syst

View full text Add to dashboard Cite

Hydrological interactions between vegetation, soil, and topography are complex, and heterogeneous in semi‐arid landscapes. This along with data scarcity poses challenges for large‐scale modeling of vegetation‐water interactions. Here, we exploit metrics derived from daily Meteosat data over Africa at ca. 5 km spatial resolution for ecohydrological analysis. Their spatial patterns are based on Fractional Vegetation Cover (FVC) time series and emphasize limiting conditions of the seasonal wet to dry transition: the minimum and maximum FVC of temporal record, the FVC decay rate and the FVC integral over the decay period. We investigate the relevance of these metrics for large scale ecohydrological studies by assessing their co‐variation with soil moisture, and with topographic, soil, and vegetation factors. Consistent with our initial hypothesis, FVC minimum and maximum increase with soil moisture, while the FVC integral and decay rate peak at intermediate soil moisture. We find evidence for the relevance of topographic moisture variations in arid regions, which, counter‐intuitively, is detectable in the maximum but not in the minimum FVC. We find no clear evidence for wide‐spread occurrence of the “inverse texture effect” on FVC. The FVC integral over the decay period correlates with independent data sets of plant water storage capacity or rooting depth while correlations increase with aridity. In arid regions, the FVC decay rate decreases with canopy height and tree cover fraction as expected for ecosystems with a more conservative water‐use strategy. Thus, our observation‐based products have large potential for better understanding complex vegetation‐water interactions from regional to continental scales.

show abstract

Section: Introductionmentioning

confidence: 87%

Characterizing the Response of Vegetation Cover to Water Limitation in Africa Using Geostationary Satellites

Küçük

Koirala

Miralles

et al. 2022

J Adv Model Earth Syst

View full text Add to dashboard Cite

show abstract

“…Climatic impacts (especially precipitation), periodical fires, and grazing by herbivores are the most important factors that shape plant community composition and structure in savannas (Skarpem, 1992). Palatable perennial grasses are generally considered an important and stable source of forage for livestock (Trollope et al., 2014; O'Connor, 2015) and large wildlife species (Schmiedel et al., 2020) in savanna systems. Heavy grazing can reduce perennial grass biomass (Díaz et al., 2007; van Coller et al., 2018), leading to conditions being favourable for the establishment of grasses with lower grazing values, as well as woody species (Schmiedel et al., 2020).…”

Section: Introductionmentioning

confidence: 99%

“…Palatable perennial grasses are generally considered an important and stable source of forage for livestock (Trollope et al., 2014; O'Connor, 2015) and large wildlife species (Schmiedel et al., 2020) in savanna systems. Heavy grazing can reduce perennial grass biomass (Díaz et al., 2007; van Coller et al., 2018), leading to conditions being favourable for the establishment of grasses with lower grazing values, as well as woody species (Schmiedel et al., 2020). Herbivore pressure in combination with changes in fire regimes (Stevens et al., 2016), climate change, and an increase in atmospheric CO 2 (Stevens et al., 2017) can lead to a shift from grasslands with scattered shrubs, to a state of increased shrub abundance, cover and biomass with a subsequent decline in perennial grass cover.…”

Section: Introductionmentioning

confidence: 99%

Response of herbaceous functional types and woody vegetation to selective shrub control on wildlife and cattle ranches in a semi‐arid savanna

Marquart,

van Coller,

van Staden

et al. 2023

Applied Vegetation Science

View full text Add to dashboard Cite

AimsShrub encroachment is a major challenge for livestock and wildlife management in semi‐arid savannas. Shrub removal by land managers is widespread, but the long‐term effects on vegetation structure and composition, which determine carrying capacity for herbivores, are poorly documented. This study aims to examine the effects of selective shrub removal to guide vegetation management in key land uses of semi‐arid African savannas.QuestionsVegetation responses were assessed across land uses and treatments to answer the following questions: (1) does shrub removal increase the frequency of palatable plants and therefore herbivore‐carrying capacity; (2) does selective shrub removal decrease woody vegetation structure 15 years after application; and (3) how do these effects differ between cattle and wildlife ranching?LocationMolopo region of the North West Province, South Africa.MethodsHerbaceous and woody vegetations were sampled within six transects each of three wildlife ranches and three cattle ranches in areas that had either been selectively shrub‐controlled with herbicides 10–15 years previously or left untreated. To quantify effects of woody shrub control on herbaceous functional‐group abundances and assemblages, tree equivalents, regrowth rate, and shrub abundance, we compared these variables across two treatments (treated and untreated) and land uses. Data were analysed using GLMMs, NMDS ordinations, PERMANOVA, and SIMPER.ResultsSelective shrub control effectively improved palatable herbaceous vegetation, especially on cattle ranches. Especially abundance of perennial grass was higher on wildlife ranches compared to cattle ranches. Tree equivalent was higher in untreated compared to treated plots, and these differences were more pronounced on wildlife ranches than on cattle ranches.ConclusionssSelective shrub removal improved the palatable herbaceous layer for both wildlife and cattle ranching and can be considered an effective management strategy in semi‐arid rangelands.

show abstract

“…Successful recruitment to the sapling bank can be rare and is usually tightly linked to rainfall (Barnes, 2001b; Fensham et al, 2017; Kraaij & Ward, 2006; Seymour & Milton, 2003) and/or drought (Van der Waal et al, 2009). Divergent strategies among tree species in response to rainfall may reduce the influence of climate on woody component structure in dry savannas (Schmiedel et al, 2021), however. For example, the saplings of long‐lived species may accumulate for many years before escaping to higher size classes (Fornara & du Toit, 2008; Seymour, 2008).…”

Section: Introductionmentioning

confidence: 99%

Mean height increase in saplings of a keystone woody savanna species over 15 years similar to that over a single season

et al. 2022

View full text Add to dashboard Cite

Woody structure, particularly that created by large trees, is crucial to savanna biodiversity pattern and process. We assessed changes in vertical and horizontal canopy over 15 years of saplings of Vachellia (Acacia) erioloba (camelthorn), a keystone species and one of the only trees to grow large in arid savanna on low rainfall areas of Kalahari sands, southern Africa. We also assessed whether the fastest growing saplings over the 2003-2004 growing season were also the fastest growing over the following 15 years. We measured height, canopy extent, and diameter of largest stem at ground level of 120 saplings of V. erioloba in November 2003, remeasuring these in March 2004. In November 2019, we were able to find 67 of these saplings, and we measured them again to assess growth between 2004 and 2019. We modeled interindividual explanatory variables for growth (i.e., measures taken in 2004 of height, diameter, number of stems, evidence of fire, and largest stem diameter). We also compared residuals of growth between 2003 and 2004 with those between 2004 and 2019, to assess whether individuals showed similar progress relative to their peers over the two periods considered. Height increase was extremely variable, but mean increase over 15 years was only 45.4 mm, similar to that measured for the 2003-2004 growing season (43.1 mm). Mean horizontal canopy showed far greater growth (mean 120.2 mm over 15 years, compared with 7.12 mm over 2003-2004) than vertical growth. Individuals that had shown the fastest increase in horizontal canopy in [2003][2004] tended to be the same individuals that grew fastest over the following 15 years, but even the highest "achievers" showed increases of only 47.2 mm and 37.5 mm year À1 in average horizontal canopy extent and height, respectively. This study demonstrates how crucial long-term studies are, particularly in arid systems.Many individuals may be trapped in the "sapling" class and could take decades to become large trees. Woody sapling growth was not cumulative, and

show abstract

Response of Kalahari vegetation to seasonal climate and herbivory: Results of 15 years of vegetation monitoring

Abstract: This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Cited by 11 publications

References 59 publications

Characterizing the Response of Vegetation Cover to Water Limitation in Africa Using Geostationary Satellites

Characterizing the Response of Vegetation Cover to Water Limitation in Africa Using Geostationary Satellites

Response of herbaceous functional types and woody vegetation to selective shrub control on wildlife and cattle ranches in a semi‐arid savanna

Mean height increase in saplings of a keystone woody savanna species over 15 years similar to that over a single season

Contact Info

Product

Resources

About